Optical fiber orientation detection method and apparatus

ABSTRACT

A method is provided for detecting an orientation of an optical fiber including a flat surface as a part of a surface of the maintaining member. The method includes directing collimated light to the optical fiber through the flat surface of the maintaining member, receiving reflected light of the collimated light by using an optical sensor device, generating a brightness distribution image according to an output signal from the optical sensor device, identifying a reference point on a brightness distribution line appearing on the generated brightness distribution image, according to a position of the brightness distribution line in relation to a target orientation for the optical fiber, the brightness distribution line detectable on the brightness distribution image in correspondence to the reflected light received by the optical sensor device, and detecting the orientation of the optical fiber according to a coordinate of the reference point on the brightness distribution image.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2012-278028, filed on Dec. 20,2012, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a method of detectingthe orientation of an optical fiber and an apparatus.

BACKGROUND

Optical communication systems have come into widespread use and varioustypes of optical modules are now in practical use. Examples of modulesplaced in practical use include modules including an optical modulator,an optical amplifier, an optical transmitter, an optical receiver, or anoptical switch.

Commercially available optical modules include often an input opticalfiber and an output optical fiber coupled thereto. The input opticalfiber is optically coupled to the input end of an optical device suchas, for example, an optical modulator, optical amplifier, opticaltransmitter, optical receiver, or optical switch in an optical module.The output fiber is optically coupled to the output end of the opticaldevice. To reduce the coupling loss of the optical module, therefore, itis desirable to precisely align the ends of the input optical fiber andoutput optical fiber to the optical device.

When an optical module to which an optical fiber (an input opticalfiber, an output optical fiber, or both) is connected is manufactured,the position of the end of the optical fiber is detected with respect toan optical device in the optical module. The position of the opticalfiber is detected by, for example, using an electronic camera tophotograph the optical fiber. The optical fiber is then alignedaccording to the detection result so as to reduce the coupling loss ofthe optical module.

As a related technology, a method is provided in which an optical partsuch as, for example, a waveguide, and an optical fiber are easilycoupled with high precision (see Japanese Laid-open Patent PublicationNo. 8-146242, for example). In another method provided, the inclinationof an end surface of a cylindrical member is highly precisely measuredrelative to the side surface of the cylindrical member (see JapaneseLaid-open Patent Publication No. 2006-214753, for example). In stillanother method provided, a charge-coupled device (CCD) camera is used toinspect a defect on a thin film (see Japanese Laid-open PatentPublication No. 7-301608, for example).

SUMMARY

According to an aspect of the invention, a method of detecting anorientation of an optical fiber that is provided in anoptical-transparent maintaining member including a flat surface as apart of a surface of the maintaining member, the method includesdirecting collimated light to the optical fiber through the flat surfaceof the maintaining member, receiving reflected light of the collimatedlight by using an optical sensor device, generating a brightnessdistribution image according to an output signal from the optical sensordevice, identifying a reference point on a brightness distribution lineappearing on the generated brightness distribution image, according to aposition of the brightness distribution line in relation to a targetorientation for the optical fiber, the brightness distribution linedetectable on the brightness distribution image in correspondence to thereflected light received by the optical sensor device, and detecting theorientation of the optical fiber according to a coordinate of thereference point on the brightness distribution image.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates the orientation of an optical fiber;

FIGS. 2A, 2B, and 2C illustrate θx, θy, and θz, which represent anorientation of the optical fiber;

FIGS. 3A and 3B illustrate an example of an optical module;

FIGS. 4A and 4B illustrate the structure of a ferrule;

FIG. 5 illustrates the structure of the orientation detecting apparatus;

FIGS. 6A and 6B illustrate a method in which an auto collimator is usedto detect the orientation of a target object;

FIG. 7 illustrate light reflected when collimated light is directed tothe optical fiber;

FIG. 8 illustrates an example of a brightness distribution imageobtained when collimated light is directed to the optical fiber;

FIGS. 9A and 9B illustrate reflection from the optical fiber andferrule;

FIGS. 10A to 10C illustrate examples of brightness distribution imagesgenerated with different θx values;

FIGS. 11A to 11C illustrate examples of brightness distribution imagesgenerated with different θy values;

FIGS. 12A to 12C illustrate examples of brightness distribution imagescreated with different θz values;

FIG. 13 illustrates the orientation of the optical fiber and theposition of a brightness distribution line;

FIG. 14 illustrates an example of a reference distribution pattern;

FIG. 15 illustrates an example of comparison;

FIG. 16 illustrates a method of calculating θx, θy, and θz according toa reference point;

FIG. 17 is a flowchart illustrating an orientation detection method inan embodiment; and

FIG. 18 is a flowchart illustrating a method of identifying thereference point.

DESCRIPTION OF EMBODIMENTS

Preliminary Consideration

To reduce the coupling loss in the optical module described in thebackground, it is desirable to appropriately adjust not only theposition of the end of the optical fiber but also its orientation. Theorientation of the optical fiber is represented by θx, θy, and θzillustrated in FIG. 1.

In FIG. 1, the optical fiber 1 is assumed to have been ideally alignedto an optical waveguide 3 formed in an optical device 2. The origin ofthe xyz coordinate system in FIG. 1 is set at the end of the opticalfiber 1. The z-axis indicates a propagation direction of opticalsignals. The x- and y-axes are each set on a plane the normal of whichis the z-axis. The x- and y-axes are mutually orthogonal. The y-axis isset in a direction perpendicular to the mounting surface of the circuitboard of the optical device 2.

θx represents a rotational angle around the x-axis. FIG. 2A illustratesa state in which the optical fiber 1 has been rotated through θx from atarget orientation. In FIG. 2A, the x-axis has been set in a directionperpendicular to the drawing sheet.

θy represents a rotational angle around the y-axis. FIG. 2B illustratesa state in which the optical fiber 1 has been rotated through θy fromthe target orientation. In FIG. 2B, the y-axis has been set in adirection perpendicular to the drawing sheet.

θz represents a rotational angle around the z-axis. FIG. 2C illustratesa state in which the optical fiber 1 has been rotated through θz fromthe target orientation. In FIG. 2C, the z-axis has been set in adirection perpendicular to the drawing sheet.

In the method in which an electronic camera is used to photograph theoptical fiber, however, it is difficult to detect θx, θy, and θz. When,for example, the optical device 2 and optical fiber 1 are photographedfrom above the optical device 2, it is difficult to detect θx and θzfrom image data obtained by the photography.

It may be possible to detect the orientation of the target object byusing an auto collimator. The auto collimator directs collimated lightto the target object and detects light reflected from the target objectby using an optical sensor device such as, for example, a charge-coupleddevice (CCD) sensor. A brightness distribution image is generatedaccording to output signals from the optical sensor device. When thisbrightness distribution image is analyzed, therefore, it may be possibleto identify the position or orientation of the target object.

When, for example, collimated light with a certain beam diameter isdirected to a flat surface of the target object, light reflected fromthe target object is also collimated light having substantially the samebeam diameter. Accordingly, a high-brightness point appears atcoordinates corresponding to a position at which the reflected light hasbeen detected. The angle of the flat surface (or the direction of thenormal to the flat surface) is detected according to the coordinates ofthe high-brightness point on the brightness distribution image and theorientation of the target objects thereby detected.

However, the optical fiber is formed in a thin, substantially rod shape.When collimated light with a certain beam diameter is directed to theoptical fiber, therefore, light rays are led in different directionsdepending on the positions on the optical fiber to which the light rayshave been directed. For this reason, a high-brightness point does notappear on the brightness distribution image. In the method in whichcollimated light reflected on a flat surface is used to detect the angleof the flat surface, it is difficult to detect the orientation of theoptical fiber (that is, the set angle of the optical fiber).

Accordingly precisely detecting the orientation of an optical fiber isdesired.

The embodiments will be described. FIGS. 3A and 3B illustrate an exampleof an optical module to which an orientation detection method in anembodiment of the present disclosure is applied. FIG. 3A illustrates anoptical module 10 as viewed from its side and FIG. 3B illustrates theoptical module 10 as viewed from above.

The optical module 10 includes an optical device chip 11. An opticaldevice is mounted on a surface of the optical device chip 11. Althoughthere is no particular restriction on the optical device, it is, forexample, an optical modulator, optical amplifier, optical transmitter,optical receiver, optical switch, or other device. When an opticalmodulator is mounted on the surface of the optical device chip 11, theoptical device chip 11 is implemented by, for example, a Low Noise chip(LN chip). In this case, for example, an interferometer, a wire throughwhich a driving signal is transferred, an electrode to which the drivingsignal is given, an optical waveguide, which is optically coupled to theinterferometer, and the like are formed on the surface of the LN chip.

An input optical fiber 12 a and an output optical fiber 12 b areattached to the optical module 10. The input optical fiber 12 a isoptically coupled to an input optical waveguide 13 a of the opticaldevice chip 11. The output optical fiber 12 b is optically coupled to anoutput optical waveguide 13 b of the optical device chip 11.

The end of the input optical fiber 12 a is accommodated in a ferrule 14a. The ferrule 14 a is secured to the optical device chip 11 with theinput optical fiber 12 a aligned to the input optical waveguide 13 a ofthe optical device chip 11. In this example, however, an auxiliarymember (jig) 15 a is attached to the surface of the optical device chip11. The ferrule 14 a is secured to the optical device chip 11 andauxiliary member 15 a with, for example, an adhesive.

Similarly, the end of the output optical fiber 12 b is accommodated in aferrule 14 b. The ferrule 14 b is secured to the optical device chip 11with the output optical fiber 12 b aligned to the output opticalwaveguide 13 b of the optical device chip 11. In this example, however,an auxiliary member (jig) 15 b is attached to the surface of the opticaldevice chip 11. The ferrule 14 b is secured to the optical device chip11 and auxiliary member 15 b with, for example, an adhesive.

In FIG. 3A, the input optical waveguide 13 a and output opticalwaveguide 13 b are not illustrated. In FIG. 3B, the auxiliary members 15a and 15 b are not illustrated. In the description below, the inputoptical fiber 12 a and output optical fiber 12 b may be referred to asthe optical fiber 12, the input optical waveguide 13 a and outputoptical waveguide 13 b may be referred to as the optical waveguide 13,and the ferrules 14 a and 14 b may be referred to as the ferrule 14.

FIGS. 4A and 4B illustrate the structure of the ferrule 14. FIG. 4A is aperspective view of the ferrule 14, and FIG. 4B is a cross-sectionalview of the ferrule 14. The ferrule 14 is formed in a substantiallycylindrical shape. However, an orientation flat 21 is formed on part ofthe side surface of the cylinder. The orientation flat 21 is a flatsurface formed on the side surface of the ferrule 14 as an aid to detectthe orientation of the ferrule 14. The ferrule 14 accommodates theoptical fiber 12 along the central axis of the cylinder. That is, theferrule 14 is an example of a maintaining member that accommodates theoptical fiber 12. In FIG. 4A, a through-hole 22 is drawn in which theoptical fiber 12 is accommodated. The ferrule 14 is made of atransparent material. An example of the material of the ferrule 14 isglass. However, the ferrule 14 and the cladding of the optical fiber 12have different refractive indexes.

Although there is no particular restriction on the optical fiber 12accommodated in the ferrule 14, the optical fiber 12 is a polarizationmaintaining fiber in this example. In this case, as illustrated in, forexample, FIG. 4B, the optical fiber 12 is accommodated in the ferrule 14so that the polarization direction of the optical fiber 12 issubstantially perpendicular to the orientation flat 21 of the ferrule14. Although there is no particular restriction on the optical fiber 12accommodated in the ferrule 14 as described above, the optical fiber 12is assumed not to be coated in this example. That is, the core andcladding of the optical fiber 12 are accommodated in the ferrule 14.

The ferrule 14, in which the optical fiber 12 is accommodated, issecured to the optical device chip 11 so that the mounting surface ofthe optical device chip 11 and the orientation flat 21 of the ferrule 14become parallel or substantially parallel to each other. Specifically,each ferrule 14 is secured to the optical device chip 11 and itscorresponding auxiliary member 15 a or 15 b with an adhesive.

FIG. 5 illustrates the structure of an orientation detecting apparatusin an embodiment of the present disclosure. The orientation detectingapparatus 30 in the embodiment includes an auto collimator 31 and aprocessor system 34. The auto collimator 31 includes a collimating unit32 and an optical sensor device 33. The collimating unit 32 includes alaser light source that generates laser light with a certain wavelengthand also includes an optical system that generates collimated light witha certain beam diameter from the laser light. The collimated lightgenerated by the collimating unit 32 is directed to the target object tobe detected. The target object to be detected is the optical waveguidefiber 12 (that is, the input optical fiber 12 a and output optical fiber12 b of the optical module 10).

The optical sensor device 33 receives the light reflected on the opticalfiber 12 where the light is the collimated light generated by thecollimating unit 32. Since the optical fiber 12 is accommodated in thetransparent ferrule 14, the optical sensor device 33 receives reflectedlight from the optical fiber 12 and reflected light from the ferrule 14.The optical sensor device 33 is implemented by, for example, a CCDsensor or a complementary metal oxide semiconductor (CMOS) sensor.

The processor system 34 includes a brightness-distribution-imagecreating unit 35 and an orientation detector 36. Thebrightness-distribution-image creating unit 35 creates a brightnessdistribution image according to the output signal from the opticalsensor device 33. The orientation detector 36 detects the orientationsof the optical fibers 12 (12 a and 12 b) according to the brightnessdistribution image created by the brightness-distribution-image creatingunit 35. The processor system 34 provides functions of thebrightness-distribution-image creating unit 35 and orientation detector36 by, for example, executing a software program. In this case, thesoftware program is stored in, for example, a memory provided in theprocessor system 34 or a memory accessible to the processor system 34.

The processor system 34 includes a brightness-distribution database 37.The brightness-distribution database 37 stores data that represents areference distribution pattern, which will be described later. Thebrightness-distribution database 37 may be disposed outside theprocessor system 34. In this case, the brightness-distribution database37 accesses the brightness-distribution database 37 and obtains thereference distribution pattern.

Although, in the example illustrated in FIG. 5, the processor system 34creates the brightness distribution image, the present disclosure is notlimited to this configuration or structure. For example, the autocollimator 31 may include a function that generates the brightnessdistribution image, and the processor system 34 may use the brightnessdistribution image generated by the auto collimator 31 to detect theorientation of the optical fiber 12. In this case, the processor system34 may lack the brightness-distribution-image creating unit 35.

The alignment apparatus 40 adjusts the positions and orientations of theoptical fibers 12 (12 a and 12 b). During this adjustment, the alignmentapparatus 40 places the optical module 10 below the auto collimator 31.That is, the optical module 10 is placed so that collimated light isdirected from above the auto collimator 31 to the optical fiber 12 andferrule 14. In the adjustment of the positions of the fibers 12 a andoutput optical fiber 12 b, the alignment apparatus 40 respectivelyaligns the ends of the fibers 12 a and 12 b to their correspondingoptical waveguides 13 a and 13 b. In the adjustment of the orientationsof the input optical fiber 12 a and input optical fiber 12 b, thealignment apparatus 40 references the detection result obtained from theorientation detecting apparatus 30.

Depending on the structure of the optical module 10, collimated lightmay be directed to the optical module 10 only from one direction. Tosimplify a manufacturing process of the optical module 10, it isdesirable to detect the orientation of the optical fiber 12 by directingcollimated light to the optical module 10 from the one direction. Forthese reasons, in the orientation detection method in the embodiment,the orientation of the optical fiber 12 is detected by directingcollimated light to the optical fiber 12 from the one direction. In thisexample, when the orientation of the optical fiber 12 is detected, theoptical module 10 is placed below the auto collimator 31 as illustratedin FIG. 3A. That is, when the orientation of the optical fiber 12 isdetected, the optical module 10 receives collimated light from above.

The orientation detecting apparatus 30 may concurrently detect theorientations of the fibers 12 a and 12 b to adjust their orientations.Alternatively, the orientation detecting apparatus 30 may detect theorientations of the fibers 12 a and 12 b one at a time to adjust theirorientations.

FIGS. 6A and 6B illustrate a method in which the auto collimator 31 isused to detect the orientation of the target object. In this example,collimated light having a certain beam diameter is directed to the flatsurface, as illustrated in FIG. 6A. In this case, light reflected fromthe target object is also collimated light having substantially the samebeam diameter. Accordingly, when the optical sensor device 33 receivesthe reflected light of the collimated light, a high-brightness pointcorresponding to the reflected light appears on the brightnessdistribution image, as illustrated in FIG. 6B. The coordinates of thishigh-brightness point correspond to the position at which the opticalsensor device 33 has detected the reflected light. Accordingly, thecoordinates of the high-brightness point represent the orientation ofthe target object. When, for example, it is assumed that the xyzordinate system illustrated in FIG. 6A has been defined and collimatedlight parallel to the y-axis is directed to the target object, thencoordinate θx in the horizontal direction on the brightness distributionimage represents an angle through which the target object has beenrotated around the x-axis. Similarly, coordinate θz in the horizontaldirection on the brightness distribution image represents an anglethrough which the target object has been rotated around the z-axis. Theauto collimator 31 is be used to detect the orientation of the targetobject in this way.

FIG. 7 illustrate light reflected when collimated light is directed tothe optical fiber 12. The optical fiber 12 is formed in a cylindrical orsubstantially cylindrical shape with a certain diameter. The collimatedlight has a certain beam diameter. Accordingly, light rays are led indifferent directions depending on the positions, on the side surface ofthe optical fiber 12, to which the light rays have been directed, asillustrated in FIG. 7. For example, reflected light of a collimatedlight ray directed to point P1 is led to angle θ1. Similarly, reflectedlight of a collimated light ray directed to point P2 is led to angle θ2,and reflected light of a collimated light ray directed to point P3 isled to angle θ3. When the optical axial direction of the optical fiber12 is the z direction, the z coordinates at points P1 to P3 are thesame.

The reflected light of the collimated light is received by the opticalsensor device 33. Specifically, the reflected light rays of thecollimated light rays are led on a single straight line on the lightreceiving surface of the optical sensor device 33. For example, thereflected light rays from points P1 to P3 are respectively led to pointsQ1 to Q3 on the optical sensor device 33. Points Q1 to Q3 are aligned ona straight line S.

Collimated light rays may be directed to positions having the samerotational angle φ illustrated in FIG. 7. Even when these collimatedlight rays are directed to different positions in the optical axialdirection (z direction in FIG. 7) of the optical fiber 12, the reflectedlight rays of the collimated light rays are led substantially in thesame direction. For example, points P2 and P4 have the same rotationalangle φ relative to the center of the optical fiber 12. In this case, areflected light ray from point P2 and a reflected light ray from pointP4 are led in the same direction. Accordingly, the reflected light rayof the collimated light ray directed to point P4 is led to a point nearpoint Q2 on the optical sensor device 33. When collimated light having acertain beam diameter is directed to the side surface of the opticalfiber 12, therefore, reflected light rays are not detected along thestraight line S on the optical sensor device 33.

FIG. 8 illustrates an example of a brightness distribution imageobtained when collimated light is directed to the optical fiber 12. InFIG. 8, high-brightness pixels are represented in black.

The brightness distribution image is created according to output signalsfrom the optical sensor device 33, as described above. The reflectedlight from the optical fiber 12 is detected by the optical sensor device33 along the straight line S. On the brightness distribution image,therefore, a brightness distribution pattern corresponding to thereflected light forms a substantially straight line. That is, asubstantially straight brightness distribution pattern is obtained onthe brightness distribution image. In the description below, a linearbrightness distribution pattern, which appears on the brightnessdistribution image due to reflected light, may be referred to as abrightness distribution line.

As described above, the optical fiber 12 is accommodated in the ferrule14. That is, the collimated light is directed through the ferrule 14 tothe optical fiber 12, as illustrated in FIG. 9A. Specifically, thecollimated light is directed to the orientation flat 21 of the ferrule14. The collimated light is assumed to be directed substantiallyperpendicular to the orientation flat 21.

When directed to the optical fiber 12, therefore, the collimated lightis also reflected by the ferrule 14 as illustrated in FIG. 9B. In FIG.9B, the solid arrows represent reflected light rays from the opticalfiber 12 and the dotted arrows represent reflected light rays from theferrule 14. The reflected light from the ferrule 14 is also led to theoptical sensor device 33. The reflected light from the optical fiber 12and the reflected light from the ferrule 14 mutually interfere. Whencollimated light is directed to the optical fiber 12, therefore, thebrightness distribution line, which appears on the brightnessdistribution image due to reflected light, has an interference fringe asillustrated in FIG. 8. The interference fringe pattern of the brightnessdistribution line is determined according to the diameter and materialof the optical fiber 12, the shape and material of the ferrule 14, andother properties.

As described above, the orientation detecting apparatus 30 in theembodiment directs collimated light to the optical fiber 12 accommodatedin the ferrule 14 and detects reflected light of the collimated light byusing the optical sensor device 33. The orientation detecting apparatus30 then creates a brightness distribution image from output signalssupplied from the optical sensor device 33. Therefore, the orientationdetecting apparatus 30 detect the orientation of the optical fiber 12according to the brightness distribution line appearing on thebrightness distribution image.

Next, relationships between the brightness distribution and theorientation of the optical fiber 12 will be described with reference toFIGS. 10A to 10C, 11A to 11C, and 12A to 12C. It will be assumed herethat the xyz coordinate system illustrated in FIGS. 1 and 2A to 2C hasbeen set. Collimated light parallel to the y-axis is assumed to bedirected to the optical fiber 12 and ferrule 14. The optical fiber 1 andoptical device 2 in FIGS. 1 and 2A to 2C correspond to the optical fiber12 (12 a and 12 b) and the optical device chip 11.

FIGS. 10A to 10C illustrate examples of brightness distribution imagesgenerated with different θx values. θx represents a rotational anglearound the x-axis as in FIG. 1. That is, θx represents an inclinationangle of the optical fiber 12 as in FIG. 2A. Specifically, θx representsan inclination angle of the optical fiber 12 relative to a plane thedirection of the normal of which is the propagation direction of thecollimated light. The brightness distribution images in FIGS. 10A to 10Chave been obtained when θy is 0 and θz is 0.

FIG. 10B illustrates a brightness distribution image generated when θxis 0. When θx is 0, this state is equivalent to a state in which theoptical fiber 12 is maintained at the target orientation with respect toangle θx. Specifically, when θx is 0, this state is equivalent to astate in which the optical fiber 12 is maintained parallel to themounting surface of the optical device chip 11. In this state, abrightness distribution line appears at the center of the brightnessdistribution image.

FIG. 10A illustrates a brightness distribution image generated when theoptical fiber 12 is inclined in the negative direction (θx=−0.5 degree).In this state, a brightness distribution line appears on the right sidewhen compared with the brightness distribution line generated when θx is0. FIG. 10C illustrates a brightness distribution image generated whenthe optical fiber 12 is inclined in the positive direction (θx=0.5degree). In this state, a brightness distribution line appears on theleft side when compared with the brightness distribution line generatedwhen θx is 0.

When θx changes, the position (coordinate of the brightness distributionimage in the horizontal direction) at which a brightness distributionline appears changes in this way. That is, the position (coordinate ofthe brightness distribution image in the horizontal direction) at whicha brightness distribution line appears is determined by θx.

FIGS. 11A to 11C illustrate examples of brightness distribution imagesgenerated with different θy values. θy represents a rotational anglearound the y-axis as in FIG. 1 or FIG. 2B. That is, θy represents anangle of the optical fiber 12 in a certain direction on a plane thedirection of the normal of which is the propagation direction of thecollimated light. The brightness distribution images in FIGS. 11A to 11Chave been obtained when θx is 0 and θz is 0.

FIG. 11B illustrates a brightness distribution image generated when θyis 0. When θy is 0, this state is equivalent to a state in which theoptical fiber 12 is maintained at the target orientation with respect toangle θy. In this state, a brightness distribution line appears so as toextend in the vertical direction (or perpendicular direction) of thebrightness distribution image.

FIG. 11A illustrates a brightness distribution image generated when θyis −10 degrees. In this state, the brightness distribution line isinclined to the right. FIG. 11C illustrates a brightness distributionimage generated when θy is 10 degrees. In this state, the brightnessdistribution line is inclined to the left.

When θy changes, the inclination of the brightness distribution linechanges in this way. That is, the inclination of the brightnessdistribution line is determined by θy.

FIGS. 12A to 12C illustrate examples of brightness distribution imagesgenerated with different θz values. θz represents a rotational anglearound the z-axis as in FIG. 1. That is, θz represents a rotationalangle of the optical fiber 12 relative to the optical axis of theoptical fiber 12, as in FIG. 2C. The brightness distribution images inFIGS. 12A to 12C have been obtained when θx is 0 and θy is 0.

FIG. 12B illustrates a brightness distribution image generated when θzis 0. When θz is 0, this state is equivalent to a state in which theoptical fiber 12 is maintained at the target orientation with respect toangle θz. Specifically, when θz is 0, this state is equivalent to astate in which the direction of a polarized wave maintained by theoptical fiber 12 matches a predetermined direction.

FIG. 12A illustrates a brightness distribution image generated when θzis −0.5 degree. In this state, a brightness distribution line appearsbelow when compared with the brightness distribution line generated whenθz is 0.

FIG. 12C illustrates a brightness distribution image generated when θzis 0.5 degree. In this state, a brightness distribution line appearsabove when compared with the brightness distribution line generated whenθz is 0.

When θz changes, the position (coordinate of the brightness distributionimage in the perpendicular direction) at which a brightness distributionline appears changes in this way. That is, the position (coordinate ofthe brightness distribution image in the perpendicular direction) atwhich a brightness distribution line appears is determined by θz.

The orientation detecting apparatus 30 in the embodiment uses therelationships described above to detect the orientation of the opticalfiber 12. Specifically, the orientation detecting apparatus 30 detectsthe orientation of the optical fiber 12 according to the position andinclination angle of the brightness distribution line that appears onthe brightness distribution image.

In the orientation detection method in the embodiment, the targetorientation of the optical fiber 12 is specified. For example, thetarget orientation of the optical fiber 12 is specified as describedbelow.

(1) The optical fiber 12 is placed on a plane that is parallel to themounting surface of the optical device chip 11. This condition isstipulating by setting θx to 0.

(2) The optical fiber 12 is placed so as to extend in the same directionas the direction in which the input optical waveguide 13 (input opticalwaveguide 13 a or output optical waveguide 13 b) of the optical devicechip 11 propagates light. This condition is stipulating by setting θy to0.

(3) The direction of the polarized wave maintained by the optical fiber12 is perpendicular to the mounting surface of the optical device chip11. This condition is stipulating by setting θz to 0.

The orientation detecting apparatus 30 detects the orientation of theoptical fiber 12 with respect to the above target orientation. In thiscase, when the orientation detector 36 detects the relative position(coordinate in the horizontal direction) of the brightness distributionline appearing on the brightness distribution image, with respect to thebrightness distribution line corresponding to the target orientationillustrated in FIG. 10B, θx be calculated. When the orientation detector36 detects the relative inclination angle of the brightness distributionline appearing on the brightness distribution image, with respect to thebrightness distribution line corresponding to the target orientationillustrated in FIG. 11B, θy be calculated. When the orientation detector36 detects the relative position (coordinate in the perpendiculardirection) of the brightness distribution line appearing on thebrightness distribution image, with respect to the brightnessdistribution line corresponding to the target orientation illustrated inFIG. 12B, θz be calculated.

FIG. 13 illustrates the orientation of the optical fiber 12 and theposition of the brightness distribution line. The line L1 represents thebrightness distribution line obtained when the optical fiber 12 ismaintained in the target orientation. As illustrated in FIG. 13, theline L1 is positioned at the center of the brightness distribution imagein the horizontal direction. The line L1 also extends on the brightnessdistribution image in the perpendicular direction. The orientationdetecting apparatus 30 is set so that when the optical fiber 12 ismaintained in the target orientation, the line L1 is obtained.

The line L2 represents the brightness distribution line obtained whencollimated light is directed to the optical fiber 12. The line L2 isobtained by having the line L1 undergo parallel displacement from apoint Q to a point R and then inclining the line L1. Paralleldisplacement from the point Q to the point R is achieved when angles θxand θz are given to the optical fiber 12. The brightness distributionline to be inclined when angle θy is given to the optical fiber 12.

Accordingly, to detect θx and θz, the orientation detecting apparatus 30detects parallel displacement from the point Q to the point R on thebrightness distribution image. In this example, the point Q is set atthe central coordinates (600, 400) of the brightness distribution image.Therefore, the orientation detecting apparatus 30 identifies thecoordinates of the point R to detect θx and θz. θx and θz will becalculated by using the point R on the non-aligned optical fiber 12which is represented by L2, and accordingly the point R will be referredto below as the reference point.

To identify the reference point described above, the orientationdetector 36 compares the brightness distribution line appearing on thebrightness distribution image with the reference distribution patternL1, which is prepared in advance. The orientation detector 36 identifiesthe coordinates of the reference point used to calculate θz and θx,according to the comparison result.

FIG. 14 illustrates an example of the reference distribution pattern.The reference distribution pattern represents a brightness distribution(interference fringe pattern) obtained when collimated light is directedto the optical fiber 12 maintained in a predetermined orientation. InFIG. 14, the vertical axis represents coordinates of the brightnessdistribution image in the perpendicular direction. In this example, thesize of the brightness distribution image is 800×1200 pixels asillustrated in FIG. 13, so 0 indicates the pixel at the lower end of thebrightness distribution image and 800 indicates the pixel at the upperend. The horizontal axis indicates brightness. In this example, thebrightness of each pixel is represented by eight-bit data (one of 0 to255).

The reference distribution pattern represents a brightness distributionobtained in correspondence to the reflected light from the optical fiber12 and the reflected light from the ferrule 14 when, for example, theoptical fiber 12 is adjusted to a target orientation. That is, thereference distribution pattern represents an interference fringe patternof a brightness distribution line obtained in correspondence toreflected light when the optical fiber 12 is adjusted to the targetorientation. The target orientation of the optical fiber 12 in thisexample is represented by θx=0, θy=0, and θz=0. In the example in FIG.13, the reference distribution pattern is the line L1.

When collimated light is directed through the orientation flat 21 of theferrule 14 to the optical fiber 12, a distribution of angles at whichreflected light rays are led is substantially symmetrical with respectto the center of the distribution, as illustrated in FIG. 9B.Accordingly, the interference fringe pattern of the brightnessdistribution corresponding to the reflected light from the optical fiber12 and the reflected light from ferrule 14 is also substantiallysymmetrical with respect to the center of the pattern. When the opticalfiber 12 is maintained in the target orientation, the interferencefringe pattern of the brightness distribution is symmetric with respectto the center of the brightness distribution image. On the referencedistribution pattern in FIG. 14, therefore, a brightness distributionimage from coordinate 400 to coordinate 800 and a brightnessdistribution image from coordinate 400 to coordinate 0 are substantiallysymmetric with each other.

The reference distribution pattern is generated in advance through, forexample, a measurement or simulation. The interference fringe pattern ofthe brightness distribution line obtained when collimated light isdirected to the optical fiber 12 is determined according to the diameterand material of the optical fiber 12, the shape and material of theferrule 14, and other properties. Data representing the referencedistribution pattern is stored in the brightness-distribution database37.

The orientation detector 36 obtains brightness distribution datarepresenting the brightness distribution line that has appeared on thebrightness distribution image. The orientation detector 36 then comparesthe brightness distribution line appearing on the brightnessdistribution image with the reference distribution pattern, asillustrated in FIG. 15. In this comparison, the orientation detector 36shifts the reference distribution pattern, for example, one pixel at atime and calculates a correlation between the interference fringe of thereference distribution pattern and the interference fringe of thebrightness distribution line for each shift. In the example in FIG. 15,when the reference distribution pattern is shifted 150 pixels, thebrightness distribution image substantially matches the referencedistribution pattern. In this case, the orientation detector 36identifies the reference point according to a shift of 150 pixels.

FIG. 16 illustrates a method of calculating θx, θy, and θz according tothe reference point. The coordinates of the reference point aredetermined according to the result of comparison between the brightnessdistribution line and the reference distribution pattern. In an example,a start point T on the brightness distribution image is firstdetermined. The start point T is an intersection between the brightnessdistribution line and a straight line representing a perpendicularcoordinate of 400. When a shift of 150 pixels has been obtained in thecomparison in FIG. 15, a point at a distance of 150 pixels from thestart point T on the brightness distribution line is identified as thereference point R.

The orientation detector 36 calculates θz and θx on the brightnessdistribution image from the coordinates of the reference point R; θz andθx are represented by θz=Kz×Rz and θx=Kx×Rx, where Rz represents thecoordinate of the reference point in the perpendicular direction, Rxrepresents the coordinate of the reference point R in the horizontaldirection, and Kz and Kx each represent a proportional coefficient.These proportional coefficients are obtained in advance through, forexample, a measurement or simulation.

The orientation detector 36 detects θy on the brightness distributionimage according to the inclination angle of the brightness distributionline. In this example, the inclination angle of the brightnessdistribution line matches θy. Accordingly, θy be detected by calculatingthe inclination angle of the brightness distribution line.

FIG. 17 is a flowchart illustrating the orientation detection method inthe embodiment. Processing in this flowchart is executed when a commandto detect the orientation of the optical fiber 12 is issued to theorientation detecting apparatus 30. The position of the optical fiber 12is assumed to have been appropriately adjusted so that the optical fiber12 and its corresponding input optical waveguide 13 are opticallycoupled before this flowchart is executed.

In S1, the auto collimator 31 uses the collimating unit 32 to directcollimated light to the optical fiber 12. Since the optical fiber 12 isaccommodated in the ferrule 14, the collimated light is directed throughthe ferrule 14 to the optical fiber 12. In this case, the collimatedlight is directed substantially perpendicular to the orientation flat 21of the ferrule 14, in which the optical fiber 12 is accommodated.

In S2, the auto collimator 31 uses the optical sensor device 33 toreceive reflected light of the collimated light. In this case, theoptical sensor device 33 receives reflected light from the optical fiber12 and reflected light from the orientation flat 21 of the ferrule 14.

In S3, the brightness-distribution-image creating unit 35 creates abrightness distribution image according to output signals from theoptical sensor device 33. When the collimated light is directed to theoptical fiber 12 (and the ferrule 14), a brightness distribution lineappears on the brightness distribution image. The brightnessdistribution line is generated from the reflected light detected in S2.

In S4, the orientation detector 36 detects the brightness distributionline appearing on the brightness distribution image generated in S3. Theorientation detector 36 also obtains data representing the coordinatesand brightness of each pixel on the brightness distribution line.

In S5, the orientation detector 36 identifies the coordinates of thereference point on the brightness distribution image according topositions of the brightness distribution line appearing on thebrightness distribution image. The method of identifying the coordinatesof the reference point according to points of the brightnessdistribution line is as described above with reference to, for example,FIGS. 14 to 16.

In S6, the orientation detector 36 detects θz and θx according to thecoordinates of the reference point. In S7, the orientation detector 36detects θy according to the inclination angle of the brightnessdistribution line on the brightness distribution image. Processing in S7may be executed between S4 and S5 or between S5 and S6.

FIG. 18 is a flowchart illustrating a method of identifying thereference point. Processing in this flowchart is an example ofprocessing in S5 in FIG. 17.

In S11, the orientation detector 36 compares the brightness distributionline extracted from the brightness distribution image with the referencedistribution pattern. Specifically, the orientation detector 36calculates a correlation between data representing the brightnessdistribution line and data representing the reference distributionpattern. When, for example, the reference distribution pattern isshifted one pixel at a time and a correlation is calculated between thebrightness distribution line and the reference distribution pattern foreach shift, a shift at which the maximum correlation value is obtainedis stored.

In S12, the orientation detector 36 compares the correlation valuecalculated in S11 (in the above example, the maximum correlation value)with a predetermined threshold. When the correlation value is larger thethreshold, in S13 the orientation detector 36 identifies the coordinatesof the reference point according to the position of the interferencefringe of the brightness distribution line.

When the correlation value is smaller than or equal to the threshold, inS14 the orientation detector 36 commands the alignment apparatus 40 tochange the value of θz. The alignment apparatus 40 adjusts the value ofθz of the optical fiber 12 in response to the command from theorientation detector 36. Processing in the orientation detectingapparatus 30 then returns to S1. Thus, after a brightness distributionline preferable in detection of the orientation of the optical fiber 12has been obtained, the orientation detecting apparatus 30 detects theorientation of the optical fiber 12.

In the orientation detection method in the embodiment, the orientationof an optical fiber that is optically coupled to an optical device maybe detected by using an auto collimator and image processing. In theorientation detection method in the embodiment, the orientation of anoptical fiber may be detected even when light is directed to the opticalfiber only in one direction.

Another Embodiment

The coordinates of the reference point R may be identified by anothermethod. For example, on the brightness distribution image, theorientation detector 36 may compare the brightness distribution linewith the reference distribution pattern illustrated in FIG. 14. In thiscomparison, the orientation detector 36 detects a pixel corresponding toa coordinate of 400 on the reference distribution pattern (or a pixelcorresponding to the point Q on the line L1 illustrated in FIG. 13) onthe brightness distribution line. The orientation detector 36 then usesthe pixel detected as described above as the reference point.

Alternatively, the orientation detector 36 may identify the referencepoint by using the symmetry of the interference fringe of the brightnessdistribution line. In this method, the orientation detector 36identifies, as the reference point, a point with respect to which theinterference fringe of the brightness distribution line is symmetrical.

In still another method, a brightness distribution image is generatedfor each of two different θz angles. For example, when collimated lightis directed to the vicinity of edges on the both sides of theorientation flat 21, a brightness distribution image is generated foreach edge. The reference point is identified according to the positionof the brightness distribution line appearing on each brightnessdistribution image.

In the embodiments described above, the ferrule 14 has been shaped in acylindrical form. However, the present disclosure is not limited to thisstructure. It suffices that the maintaining member that accommodates theoptical fiber has a flat surface as at least part of the surface of themaintaining member.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although the embodiments of the presentinvention have been described in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention.

What is claimed is:
 1. A method of detecting an orientation of anoptical fiber that is provided in an optical-transparent maintainingmember including a flat surface as a part of a surface of themaintaining member, the method comprising: directing collimated light tothe optical fiber through the flat surface of the maintaining member;receiving reflected light of the collimated light by using an opticalsensor device; generating a brightness distribution image according toan output signal from the optical sensor device; identifying a referencepoint on a brightness distribution line appearing on the generatedbrightness distribution image, according to a position of the brightnessdistribution line in relation to a target orientation for the opticalfiber, the brightness distribution line detectable on the brightnessdistribution image in correspondence to the reflected light received bythe optical sensor device; and detecting the orientation of the opticalfiber according to a coordinate of the reference point on the brightnessdistribution image.
 2. The method according to claim 1, wherein thecoordinate of the reference point is identified by comparing thebrightness distribution line with a target distribution patternrepresenting a predetermined brightness distribution for the targetorientation.
 3. The method according to claim 2, wherein the targetdistribution pattern represents a brightness distribution obtained whenthe collimated light is directed to the optical fiber maintained in thetarget orientation.
 4. The method according to claim 1, wherein arotational angle of the optical fiber around an optical axis of theoptical fiber is detected according to the coordinate of the referencepoint.
 5. The method according to claim 1, wherein an inclination angleof the optical fiber is detected relative to a plane, a direction of anormal of the plane being a propagation direction of the collimatedlight, according to the coordinate of the reference point.
 6. The methodaccording to claim 1, wherein an angle of the optical fiber is detectedrelative to a certain direction on a plane, a direction of a normal ofthe plane being a propagation direction of the collimated light,according to an inclination angle of the brightness distribution line onthe brightness distribution image.
 7. An apparatus that detects anorientation of an optical fiber that is provided in anoptical-transparent maintaining member including a flat surface as apart of a surface of the maintaining member, the apparatus comprising:an optical system configured to direct collimated light to the opticalfiber through the flat surface of the maintaining member and to receivereflected light of the collimated light; and a computing processingsystem to: calculate a brightness distribution image according to anoutput signal from the optical sensor device; and identify a referencepoint on the brightness distribution image according to a position of abrightness distribution line, the brightness distribution line beingformed on the brightness distribution image in correspondence to thereflected light received by the optical sensor device, and detect theorientation of the optical fiber according to a coordinate of thereference point on the brightness distribution image.